It's just shows how many shares were exchanged traded that were not immediately accounted for or settled. It doesn’t mean that they won't settle in a few days. Not all trades are electronic sometimes…..further sometimes a MM has naked issue a few shares to cover a transaction etc, all the course of making a market. There is a lot of reasons you might see numbers on this list, but unless it was absorbingly huge for days and days then it's nothing to be concerned of……